[libc] Fix hanging test on NVPTX due to lack of warp sync

[jhuber6]

Summary

Previously this wasn't implemented because it's effectively a no-op.
However, this should be safe to emit on sm_60 architectures. It's
important because it carries semantic importance for whether or not
something can be moved. So we should always emit this instrinsic.

libc/src/__support/GPU/nvptx/utils.h

#else
   return lane_mask & __nvvm_vote_ballot(x);
 #endif
 }
 /// Waits for all the threads in the block to converge and issues a fence.
 [[clang::convergent]] LIBC_INLINE void sync_threads() { __syncthreads(); }
 
 /// Waits for all threads in the warp to reconverge for independent scheduling.
 [[clang::convergent]] LIBC_INLINE void sync_lane(uint64_t mask) {
-#if __CUDA_ARCH__ >= 700
   __nvvm_bar_warp_sync(mask);
-#else
-  (void)mask;
-#endif
 }
 
 } // namespace gpu
 } // namespace __llvm_libc
 
 #endif